Protective coating, a coated member having a protective coating as well as method for producing a protective coating

ABSTRACT

The invention relates to a protective coating, having the chemical composition C a Si b B d N e O g H l Me m , wherein Me is at least one metal of the group consisting of {Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, Y, Sc, La, Ce, Nd, Pm, Sm, Pr, Mg, Ni, Co, Fe, Mn}, with a+b+d+e+g+l+m=1. According to the invention, the following conditions are satisfied: 0.45≦a≦0.98, 0.01≦b≦0.40, 0.01≦d≦0.30, 0≦e≦0.35, 0≦g≦0.20, 0≦1≦0.35, 0≦m≦0.20. The invention relates also to a coated member having a protective coating, as well as to a method for producing a protective coating, in particular a multilayer film for a member.

TECHNICAL FIELD

The present invention relates to a protective coating for a memberexcellent in sliding characteristics and improved heat resistance, whichis produced by forming a hard film on a member required to have abrasionresistance and sufficient high-temperature oxidation resistance, to acoated member having a protective coating such as cutting tools, molds,forming tools, engine parts, gas turbines and the like, and also to amethod for producing a protective coating, in particular a multilayerfilm for a member.

BACKGROUND ART

Slide members are often coated with nitride coatings like CrN or TiN,however more and more also diamond like carbon (DLC) are applied. It isconsidered useful for coating slide members, as readily providing asmooth surface and excellent in frictional characteristics. For example,Patent Reference 1 discloses a technique of forming a DLC film of thetype a-C:H on a metal substrate. Patent Reference 2 describes amodification of a-C:H coatings by incorporation of different metals. Thecoatings are termed as a-C:H:Me coatings. Patent Reference 3 hasrealized improved the heat resistance and increased hardness of a DLCfilm by defining the content of the hydrogen content in the film at alow level ca. 5 at %. Patent Reference 4 and Patent Reference 5 disclosea DLC film containing Si in the carbon film.

Patent Reference 6 shows the modification of optical properties of a-C:Hcoatings by incorporation of silicon or boron.However, since the coatings mentioned in Patent References 1 to 6 arebased on carbon with some alloying elements like hydrogen and/or metal,or silicon or boron, the improvement in the heat resistance thereof islimited: to ca. 350-400° C. in the phase stability and to ca. 400-500°C. concerning the oxidation in air.

Contrary to this, the applicant of the present invention has proposed anSi (BCNO)-based film as in Patent Reference 7, for enhancing the heatresistance thereof and further increasing the hardness thereof.Accordingly, the abrasion resistance and the heat resistance of the filmfor use for cutting tools and abrasion-resistant members have beendrastically enhanced. Over Patent Reference 7, the present invention isto enhance not only the abrasion resistance and the heat resistance butalso the sliding characteristics of the film.

PRIOR ART REFERENCES Patent References

[Patent Reference 1] DD 258341 [Patent Reference 2] DE 32 46 361 A1[Patent Reference 3] EP-A-1 266 879 [Patent Reference 4] EP-A-1 783 349[Patent Reference 5] WO 97/12075 [Patent Reference 6] WO 00/56127[Patent Reference 7] EP-1 783 245

SUMMARY OF THE INVENTION Problems to be Solved

For automotive applications the CO₂ emissions have to be reduced. Oneway to achieve this is to reduce the friction loss in the engine andtransmission. This can be realized by coating parts like, tappets,injection system parts and piston rings or liners.

However traditional DLC coatings show some limitations in the heatresistance.Another example for the requirement to improve the properties ofclassical DLC coatings is in the field of cutting technology. The recenttendency is directed toward short-time operation under high-efficiencyworking condition for shortening the production time. Accordingly, thecutting speed is accelerated and the feeding amount is increased formore advanced high-efficiency operation than conventionally. Forexample, cutting speed acceleration may increase the working heat andthe tools may be more greatly damaged due to the heat. On the otherhand, when the feeding amount is increased, the interfacial pressurebetween the tool and the subject being worked increases, thereforecausing early-stage abrasion under the increased interfacial pressure.In addition to this, also the reduction of the amount of lubricant isone important goal in modern production. Thus the friction especially inthe areas of chip transport has to be decreased.Though there may be some differences in any case, the influence ofworking heat is being larger than under conventional working conditions,and it is indispensable to improve the heat resistance and the oxidationresistance of tools and the films to coat tool surfaces. In addition,also needed are physical properties of high hardness and high lubricityso as to inhibit the abrasion occurring under high interfacial pressure.Accordingly, an object of the invention is also to provide a multilayerfilm coated member, which is coated with a hard film having lubricationcharacteristics on a similar level as that of conventional DLC andhaving sufficient high hardness and sufficient high heat resistance, andto provide a method for producing it.

Means for Solving the Problems

The invention relates to a coated member, which is coated with a hardfilm comprising carbon, silicon and boron as the main ingredients.

Thus, a protective coating is provided, having the chemical compositionC_(a)Si_(b)B_(d)N_(e)O_(g)H_(l)Me_(m), wherein Me is at least one metalof the group consisting of {Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, Y, Sc,La, Ce, Nd, Pm, Sm, Pr, Mg, Ni, Co, Fe, Mn) with a+b+d+e+g+l+m=1.According to the invention, the following conditions are satisfied:0.45≦a≦0.98, 0.01≦b≦0.40, 0.01≦d≦0.30, 0≦e≦0.35, 0≦g≦0.20, 0≦l≦0.35,0≦m≦0.20.As clearly disclosed be the aforementioned formula, additional modifyingelements such as nitrogen and oxygen may be contained in the film. Aslater disclosed in the present description of the invention, some metalelements might be also included, especially if they are necessary toproduce sufficient high quality targets for the film deposition. Causedby the deposition method some hydrogen is mostly incorporated in thecoatings. Other impurities from the manufacturing of the targets (e.g.In) might be incorporated too. If a sputtering process is used for thecoating process also residue sputtering gas (e.g. Ar) might be included.Since the film contains silicon and boron, it becomes more stable inheat resistance than carbon containing coatings having only silicon oronly boron, or only metal respectively. That is, its heat resistance isdrastically enhanced and the film can exhibit sufficient heat resistanceeven under service environments that are more sever. In addition, sincethe film contains amorphous carbon suitably, its lubricationcharacteristics are excellent.

The existence of free amorphous carbon in the coating is important, thatmeans the existence of carbon which is not chemically bonded to siliconor boron. The carbon atoms are bonded to each other forming an own phasein the film. To characterize this, Raman spectrometry has proven to be asuitable method. The peak detected between 1300 and 1600 cm⁻¹ in Ramanspectrometry is one derived from amorphous carbon. A simple way toincrease the carbon content in the coating is the sputtering of at leastsilicon and boron containing target. During film formation, a definitehydrocarbon-based gas can be used to adjust the C content of the formedfilm, in which, therefore, the C elements bond to each other, notbonding to any other element (excluding hydrogen) if a sufficient highcarbon content is reached, in particular a certain amount of carbon isnot bonded to silicon and boron thus forming C—C bonding. This isconfirmed from the data in Raman spectrometry where C—C bond isdetected.

If between the substrate and the hard film, the member has an additionalhard film comprising at least two metal ingredients selected from Al,Ti, Cr, Nb, W, V, Zr, Hf, Ta, Mg, Mo Y, Sc, La, and lanthanides like Ce,Pr, Nd, Pm, Sm and at least one non-metallic ingredient selected from N,C, O; Si, B, and S, and the additional hard film forms a multilayerstructure along with the above-mentioned hard film A. Accordingly, theadhesion of the hard film A to the substrate is enhanced, and the hardfilm A can fully exhibit its properties.

Furthermore the adhesion of the coatings can be tailored also bydepositing a metallic interlayer (e.g. Cr or TiSi) at the substratesurface before the hard film A is deposited.

In the multilayer film coated member of the invention, as coated withhard films, the film has greatly enhanced lubricity and heat resistance.The invention provides not only the hard film A as the only one coatingat the functional surface, also the multilayer film coated member coatedwith a hard film A, and a method for producing it.

Special embodiments of coatings according to the invention are shown inFIG. 1 a and FIG. 2. In FIG. 1, the hard film A and the hard film B bothare single layers, and the coated member has a two-layer structure. Thehard film A is positioned on the outermost surface side of the member.In FIG. 2, the hard film A and the hard film B both have a multilayerstructure. The hard film A is positioned on the outermost surface sideof the member.

The method for producing a multilayer film coated member of theinvention is a method suitable for coating members with the film havingthe above-mentioned characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a typical embodiment of the present invention having asingle layer structure.

FIG. 1 a shows a typical layer structure of a film-coated member of atwo-layer structure.

FIG. 2 shows a typical layer structure of a film-coated member of amultilayer structure.

FIG. 3 shows one example of an apparatus used in film formation for afilm coated member of the invention.

FIG. 4 is a scanning electromicroscopic picture of a cross section of acoated member after heat treatment in Example 1 of the invention.

FIG. 5 is a scanning electromicroscopic picture of a cross section of acoated member after heat treatment of a conventional Example 38 knownfrom the state of the art.

FIG. 6 shows the data of Raman spectrometry in Example 1 of theinvention.

FIG. 1 shows a typical embodiment of the present invention having asingle layer structure, wherein the single layer is a CSiBNOHMe layer.In a special embodiment, a coating according to FIG. 1 may have acomposition of C_(0.65)Si_(0.20)B_(0.08)N_(0.05)O_(0.02). The 600 nmthick coating has for example a nanohardness of 2100+/−100. The coatingwere X-ray amorphous, e.g. no refractions peak from the coating materialwere detected. The stress measured by the bending method of thesubstrate (cemented carbide) was about 1.2 GPa.

In the following a more detailed discussion is made about themeasurement to show the free carbon content. Regarding for example aRaman spectrum, Ix indicates the peak resulting from amorphous carbon.It is known that the peak intensity varies depending on the filmthickness, and therefore, it is impossible to define the existingabsolute amount of amorphous carbon in the film from the peak intensity.Regarding films having the same amount of amorphous carbon existingtherein but having a different thickness, a thicker film tends to give ahigher peak intensity. Accordingly, a method to try to eliminate thethickness dependence of the peak intensity must be used. For this, themaximum intensity Iy in the background in the spectrometry is used, andthe existing amount of amorphous carbon is defined relatively to theintensity ratio of the peak intensity of amorphous carbon at Ix to themaximum intensity Iy in the background. Iy is the maximum intensity inthe background, and like Ix, its intensity varies depending on the filmthickness. A thicker film gives higher Ix and Iy, and it is consideredthat the ratio Ix/Iy defines the existing amount of amorphous carbonrelatively to it.

Within the limitation of the described method the following findingswere made. Al least, satisfying 3.2≦Ix/Iy, the film has the effect oflubricity characteristics. When Ix/Iy<3.2, then the relative existingamount of amorphous carbon in the film is small, and therefore the filmcould not has a lower lubricating effect. When Ix/Iy>8.0, then therelative existing amount of amorphous carbon in the film is large, andtherefore the heat resistance of the film is lower with the result thatthe film use is more limited, however the lubrication properties and theheat resistance are improved against conventional DLC films. Since forthe deposition of the examples a hydrocarbon-based gas is used in filmformation, it has been confirmed that the C—H bond is also detected inthe film. FIG. 6 shows an example of the data of Raman spectrometry.

For the Raman spectrometry, used was a microlaser Raman spectrometer bySeki Technotron. The assay condition is as follows:

(Assay Condition)

Solid laser wavelength for excitation: 532 nm.

Detector: cooled CCD multichannel.

Spectrometer: Chromex's 250-is Imaging Spectrograph.

Run time: 60 seconds.

Sample condition: room temperature, in air.

In the embodiment of the hard film A containing oxygen, the oxygenconcentration in the film is preferably so controlled as to be thehighest in the region near to the surface layer falling from theoutermost surface layer to the range of at most 500 nm in the filmthickness direction, from the viewpoint of the lubricity and theoxidation resistance of the film under abrasive environments.Preferably, oxygen exists in the film as oxides with silicon or boron.In case where oxygen exists in the film as its solid solution, then itmay form silicon oxide and boron oxide, for example, during operationresulting in higher temperatures in the contact zone of the wear couple.In such a case, the ingredients constituting the member of the frictioncounter part may diffuse inside the film, thereby often causing meltfusion and worsening the mechanical properties of the film. Therefore,it is desirable that oxygen exists in the film in the form of oxidestherein.

If the sputtering is done from a silicon and boron containing target(e.g. SiC/BN mixtures), than for controlling the ratio of Ix/Iy, theratio of the flow rate, Fy, of the reaction gas, hydrocarbon-based gas(e.g. C₂H₂), to the flow rate, Fx, of the process gas argon in filmformation, Fy/Fx is controlled for example to 0.007≦Fy/Fx≦0.50.Preferably, the film formation pressure in the stage is controlled to bewithin a range of approximately from 0.01 Pa to 3.0 Pa. WhenFy/Fx<0.007, then the flow rate of the hydrocarbon-based gas is low,therefore resulting in IX/Iy<3.2. As a result, the existing amount ofamorphous carbon in the film reduces and the film could not havesufficient lubricity characteristics. On the other hand, whenFy/Fx>0.50, then Ix/Iy>8.0 with the result that the use of the film ismore limited to lower temperature use, however showing still improvedheat resistance. Accordingly, the ratio Fy/Fx is preferentiallycontrolled to 0.007≦Fy/Fx≦0.50.

As the hydrocarbon-based gas, herein usable is methane acetylene,benzene, or methylbenzene or, and acetylene is preferred.

The main role of the hard film B in the invention of the two-layerstructure, is to combine the properties of the hard film A with theproperties of the hard film B. The hard film A and the hard film B eachmay have a multilayer structure showing in FIG. 2. For example, the hardfilm A is CSiB, and it may have a multilayer structure in which the Ccontent is increased in the area near the surface layer thereof. Thehard film B may have a multilayer too, e.g. structure of(TiAl)N/(TiSi)N. In this structure, (TiSi)N is applied between the hardfilm. A and (AlTi)N, thereby increasing the abrasion resistance and theadhesiveness of the multilayer film. As the case may be, the proportionof the hard film A to the entire multilayer film could not be increasedsince the hard film A may increase the residual compression stress ofthe multilayer film; and in such a case, the hard film B is thickened.Regarding the ratio of the hard film A to the hard film B, theproportion of the hard film A is preferably from 2% to 50% relative tothe entire multilayer film taken as 100%. In order to make the hard filmA to exhibit sufficiently its characteristics, the hard film B must haveexcellent adhesion strength to the surface of the substrate.

In the invention, the hard film A may be formed according to asputtering method using RF. In this case, preferably used is a compositetarget of silicon carbide and boron nitride; however, silicon carbideand boron nitride may be disposed in different coating sources, and thetwo may be sputtered at the same time to form the hard film A.

Other, not only limited to the following PVD-method, magnetronsputtering methods are usable. e.g. at DC sputtering or pulsedsputtering including High Power Pulsed Magnetron Sputtering fromcomposite targets like carbon targets with inserts made of SiC, B₄C andthe reactive gases containing nitrogen.Also arc evaporation methods are possible by alloying carbon cathodeswith Si and boron and/or the use of appropriate reactive gasescontaining boron or silicon to deposit a coating according theinvention.Another simple method to deposit such coatings are pure CVD and PE-CVDmethods by using appropriate precursors containing at least carbon,silicon and boron.

In one preferred method of forming the multilayer film, the hard film Ais formed according to a sputtering method and the hard film B is formedaccording to an arc ion plating method (AIP method) and/or a sputteringmethod. For example, in FIG. 1 a, it is important that the film 3 of thehard film B has an enhanced adhesion strength to the substrate 2, andtherefore, an AIP method is preferred for the interfacial area betweenthe substrate 2 and the film 3. The other area than the interfacial areamay be formed according to a sputtering method for further enhancing theabrasion resistance of the formed film. The method may be combined withan AIP method. The hard film A of the film 4 is coated according to asputtering method. Regarding the coating sources and the bias power inthe sputtering method and the bias power in the AIP method in thecoating film formation, a high-frequency power or a direct current powermay be applied, but from the viewpoint of the stability in the coatingprocess, a high-frequency power is used for the sputtering power. As thebias power, more preferred is a high-frequency bias power inconsideration of the electroconductivity of the hard film and of themechanical properties of the hard film.

FIG. 3 is a graphic view showing the structure of a coating apparatus 13for coating the substrate of the invention. The coating apparatus 13comprises a vacuum chamber 10; four coating sources 5, 6, 7 and 8; andtheir shutters 14, 15, 16 and 17. In this, 5 and 7 each are an RFcoating source; and 6 and 8 each are an arc source. Each coating sourcehas its shutter, which individually shuts the coating source. Theshutters are driven independently of each other, therefore capable ofindividually shutting the respective coating sources. Accordingly,during the coating process, it is unnecessary to temporarily stop thecoating source. A process gas of argon and a reaction gas of N₂, O₂ orC₂H₂ are fed into the vacuum chamber 10, which therefore has a vaporinlet port 12 provided with a switching mechanism. The substrate holder11 provided with a rotating mechanism is connected with a direct current(DC) bias power or high-frequency (RF) bias power 9. Regarding thecoating method with the films, one preferred embodiment of the movingmechanism of the coating apparatus 13 and the coating process isdescribed below.

(1) Cleaning:

After held by the substrate holder 11, the substrate 2 is heated at 250°C. to 800° C. During this, all the source shutters are kept shut. Thesubstrate is cleaned with ions by applying a pulse bias voltage theretofrom the bias power 9.

(2) Coating with hard film B:

After the substrate is thus cleaned, the shutters 15 and 17 for the arcsources 6 and 8 are opened, and the substrate is coated with a hard filmB. The hard film B may be formed according to a DC sputtering method ora DC-AIP method. The DC bias voltage to be given for film formation ispreferably from about 10 V to 400 V. As the case may be, a bipolar pulsebias voltage may also be employed. The frequency in this stage ispreferably within a range of from 0.1 kHz to 300 kHz, and the positivebias voltage is preferably within a range of from 3 V to 100 V. Thepulse/pause ratio may be within a range of from 0.1 to 0.95. During theformation of the hard film B, the RF coating sources 5 and 7 are drivenwhile the shutters 14 and 16 are kept shut. This is for the purpose ofremoving the impurities such as oxides from the target surface. Afterthe formation of the hard film B, the shutters 14 and 16 are opened, andthe RF coating sources 5 and 7 are simultaneously driven to start thenext film formation.

(3) Coating with hard film A:

The hard film A, consisting at least of CSiB, is formed from the RFmagnetron sources 5 and 7. Specifically, the RF magnetron sources 5 and7 are preferably a composite target material of silicon carbide andsilicon nitride. The surface side of the hard film A may contain alarger amount of carbon by supplying the process gas of acetylene or thelike to the vacuum chamber 10 via the vapor inlet port 12. Preferably,the carbon content in the hard film A is higher in the area nearer tothe surface side, as contributing toward enhancing the slidingcharacteristics of the film.

The coatings show typical harnesses of 1500 to 3500 and intrinsicmacroscopic stresses measured by bending test on cemented carbide of:−0.5 to −3.5 GPa (coating thickness of ca. 1.5 um).All coatings are X-ray amorphous.If a single layer film A will be directly coated at the substrates thena similar coating procedure excluding the deposition of film B is made.Another example is to deposit instead the nitride coatings metallicinterlayers before the film A is deposited.Also multilayers with more than two layers can be deposited byintermediate depositing of the film B and film B. If the sources fortraditional hard coatings like AlTiN, e.g. AIP and theSources for the film A, e.g. sputtering sources are running at the time,than nanomultilayers are generated by moving the substrates from sourcetype for the film B to the source type of film A.

The invention is described with reference to Examples hereinunder.

Example 1

For evaluating the physical properties of the hard film A of theinvention, a substrate was coated with a hard film using hard metalcontaining Co content 3% by weight or more and less than 12% by weightaccording to the coating method mentioned below. In most cases for theinvestigation a film B were first deposited. This was done, to showdirect the influence of such a film A to protect at a substrate (herethan the hard film B).

The coating method comprises a first step of heating a tool at 500° C.;a second step of ion-cleaning the tool for about 30 minutes by applyingthereto a pulse bias voltage having a negative voltage of 200 V, apositive voltage of 30 V, a frequency of 20 kHz and a pulse/pose ratioof 4; a third step of coating the tool with (AlTi)N from an arc source;a fourth step of cleaning the target surface by discharging thesputtering target while the shutters are closed and while the tool iskept coated with (AlTi)N from the arc source; a fifth step of coating ofthe hard film A by RF sputtering coating from an RF magnetron source,using a target of BN/SiC in a mixed ratio by mol of 1/3; and a sixthstep of coating of the hard film A in RF+DC by applying a DC bias havinga negative voltage of 50 V to the sample in addition to the RF biasthereto. According to the process of the above first to sixth steps, thetool was coated. In the sixth step, acetylene as the reaction gas wasintroduced into the chamber along with the process gas Ar thereinto, asa mixed gas of Ar+C₂H₂, and the ratio was controlled to be Fy/Fx=0.05.Finally, the laminate structure was comprised of (AlTi) N and of thehard film A as laminated in that order, and the film thickness was about3 μm. The sample coated according to the first coating method is Example1 of the invention. The composition of the hard film 2 in Example 1 waschanged variously, thereby producing samples of Example 2 to Example 36of the invention. The ratio (Fy/Fx) of the mixed gas of Ar+C₂H₂ to beintroduced into the chamber was changed variously, thereby producingsamples of Example 2 to Example 7 and 35 to 36 of the invention.

The details of those Examples are shown in Table 1.

TABLE 1 Special embodiments according to the invention as well examplesknown from the state of the art. Sample No. Hard film B Hard film AFy/Fx Ix/Iy Invention 1 (Al0.6Ti0.4)NSi(0.21)B(0.07)N(0.06)C(0.60)O(0.06) 0.05 3.87 2 (Al0.6Cr0.4)NSi(0.16)B(0.05)N(0.04)C(0.71)O(0.04) 0.10 4.28 3 (Al0.6Cr0.4)NSi(0.16)B(0.04)N(0.04)C(0.73)O(0.03) 0.15 4.87 4 (Al0.6Cr0.4)NSi(0.15)B(0.03)N(0.04)C(0.76)O(0.02) 0.20 5.43 5 (Al0.6Cr0.4)NSi(0.14)B(0.02)N(0.04)C(0.78)O(0.02) 0.30 6.02 6 (Al0.6Cr0.4)NSi(0.13)B(0.02)N(0.04)C(0.79)O(0.02) 0.40 6.85 7 (Al0.6Cr0.4)NSi(0.12)B(0.02)N(0.04)C(0.81)O(0.01) 0.45 6.88 8(Al0.6Ti0.4)N/(Ti0.8Si0.2)N Si(0.20)B(0.08)N(0.06)C(0.62)O(0.04) 0.053.57 9 (Al0.6Ti0.4)N/(Cr0.9Si0.1)NB Si(0.22)B(0.08)N(0.07)C(0.59)O(0.04)0.05 3.92 10 (Al0.5Ti0.4Cr0.1)N Si(0.21)B(0.08)N(0.05)C(0.61)O(0.05)0.05 4.24 11 (Al0.5Ti0.4Nb0.1)N Si(0.19)B(0.08)N(0.06)C(0.60)O(0.06)0.05 3.43 12 (Al0.5Ti0.4Si0.1)N Si(0.17)B(0.06)N(0.08)C(0.64)O(0.05)0.05 3.99 13 (Al0.5Ti0.4W0.1)N Si(0.20)B(0.08)N(0.06)C(0.62)O(0.04) 0.054.43 14 (Al0.5Ti0.4W0.1)(SN) Si(0.24)B(0.07)N(0.05)C(0.58)O(0.06) 0.053.92 15 (Al0.7Cr0.3)N Si(0.25)B(0.06)N(0.05)C(0.61)O(0.03) 0.05 3.74 16(Al0.6Cr0.3Si0.1)N Si(0.19)B(0.09)N(0.06)C(0.62)O(0.04) 0.05 3.33 17(Al0.6Ti0.4)N Si(0.20)B(0.09)N(0.05)C(0.62)O(0.04) 0.05 3.29 18(Al0.6Ti0.4)N Si(0.18)B(0.08)N(0.07)C(0.62)O(0.05) 0.05 4.03 19(Al0.6Ti0.4)N Si(0.24)B(0.05)N(0.03)C(0.65)O(0.03) 0.05 3.67 20(Al0.6Ti0.4)N Si(0.26)B(0.06)N(0.05)C(0.59)O(0.04) 0.05 3.88 21(Al0.5Ti0.5)ON Si(0.22)B(0.06)N(0.06)C(0.62)O(0.04) 0.05 3.44 22(Ti0.9Nb0.1)CN Si(0.16)B(0.05)N(0.08)C(0.66)O(0.05) 0.05 4.56 23(Ti0.8Si0.2)N Si(0.24)B(0.06)N(0.05)C(0.59)O(0.06) 0.05 4.63 24(Ti0.9W0.1)N Si(0.21)B(0.07)N(0.05)C(0.63)O(0.04) 0.05 3.75 25(Cr0.3Al0.6W0.1)N Si(0.22)B(0.09)N(0.07)C(0.59)O(0.03) 0.05 3.49 26(Cr0.9Si0.1)BO Si(0.23)B(0.09)N(0.08)C(0.56)O(0.04) 0.05 3.39 27(Cr0.9Nb0.1)N Si(0.22)B(0.07)N(0.06)C(0.61)O(0.04) 0.05 4.27 28(Cr0.9W0.1)CN Si(0.25)B(0.05)N(0.04)C(0.62)O(0.04) 0.05 3.77 29(W0.4Si0.6)C Si(0.26)B(0.05)N(0.04)C(0.60)O(0.05) 0.05 3.79 30(Nb0.4Si0.6)C Si(0.17)B(0.06)N(0.07)C(0.66)O(0.04) 0.05 3.50 31(Ti0.9V0.1)N Si(0.20)B(0.07)N(0.05)C(0.64)O(0.04) 0.05 4.22 32(Ti0.4Al0.5Mo0.1)N Si(0.25)B(0.05)N(0.05)C(0.62)O(0.03) 0.05 3.88 33(Ti0.9Zr0.1)N Si(0.19)B(0.06)N(0.06)C(0.65)O(0.04) 0.05 4.09 34(Ti0.4Al0.5V0.1)N Si(0.18)B(0.08)N(0.06)C(0.63)O(0.05) 0.05 4.11 35(Al0.6Ti0.4)N Si(0.04)B(0.03)N(0.05)C(0.87)O(0.01) 0.55 8.18 36(Al0.6Ti0.4)N Si(0.03)B(0.03)N(0.03)C(0.90)O(0.01) 1.00 8.76 Comparison37 (Al0.5Ti0.5)N/TiSiN — — — 38 (Al0.5Ti0.5)N/TiBN — — — 39(Al0.6Ti0.4)N Si(0.25)B(0.25)N(0.2)C(0.25)O(0.05) — 2.98 40(Al0.6Ti0.4)N Si(0.15)B(0.35)N(0.3)C(0.15)O(0.05) — 2.11 41(Al0.6Cr0.3Si0.1)N Si(0.43)B(0.10)N(0.11)C(0.25)O(0.11) — 3.12 42 — DLC— — 43 — DLC(H2 free) — —By Table 2, the respective friction coefficients and oxidation thicknessof the examples given in Table 1 are shown.

TABLE 2 Friction coefficients and oxidation thickness of the examplesgiven in Table 1. Coating thickness of the invented film A ca. (600 +/−100) nm. Friction coefficient Oxidation Room thickness Sample No. temp.300 deg. 500 deg. (nm) Invention 1 0.25 0.25 0.24 98 2 0.22 0.19 0.24154 3 0.23 0.18 0.24 158 4 0.24 0.27 0.22 156 5 0.22 0.21 0.23 172 60.23 0.24 0.19 166 7 0.27 0.28 0.28 185 8 0.23 0.28 0.27 102 9 0.28 0.190.21 100 10 0.21 0.21 0.26 130 11 0.17 0.23 0.27 99 12 0.26 0.27 0.26142 13 0.27 0.27 0.22 128 14 0.19 0.29 0.23 78 15 0.23 0.27 0.25 89 160.24 0.20 0.27 134 17 0.28 0.23 0.20 154 18 0.19 0.24 0.26 121 19 0.270.21 0.25 118 20 0.26 0.28 0.24 102 21 0.26 0.26 0.25 87 22 0.27 0.250.25 126 23 0.28 0.26 0.27 122 24 0.26 0.27 0.23 106 25 0.27 0.26 0.26138 26 0.26 0.27 0.27 107 27 0.25 0.27 0.26 98 28 0.24 0.28 0.23 80 290.24 0.25 0.24 108 30 0.25 0.27 0.27 146 31 0.26 0.25 0.24 135 32 0.270.24 0.28 129 33 0.28 0.23 0.27 119 34 0.21 0.22 0.23 137 35 0.27 0.250.35 488 36 0.26 0.24 0.41 527 Comparision 37 0.78 0.68 0.62 874 38 0.710.57 0.28 1868 39 0.28 0.43 0.55 — 40 0.33 0.43 0.51 — 41 0.47 0.39 0.35— 42 0.03 0.03 0.54 — 43 0.02 0.04 0.36 —In addition to the special embodiments according of the inventionaccording to table 1, also single-coating properties of a variety ofcoated films in accordance with the present invention have beeninvestigated which results are shown in Table 3 by embodiments I to V.

TABLE 3 Additional embodiments according to the invention. FrictionCoefficient Friction Friction Room Coefficient Coefficient Oxidatio 

No. Chemical Composition Temperature 300° C. 500° C. Thicknes 

I Si_(0.15)B_(0.05)N_(0.05)C_(0.6)H_(0.1)O_(0.05) 0.18 0.20 0.24 148 IISi_(0.25)B_(0.05)N_(0.1)C_(0.55)H_(0.03)O_(0.02) 0.22 0.24 0.26 103 IIISi_(0.2)B_(0.1)N_(0.1)C_(0.55)H_(0.02)O_(0.02)Ti_(0.01) 0.20 0.19 0.20160 IV Si_(0.16)B_(0.05)N_(0.1)C_(0.55)H_(0.02)O_(0.02)Ti_(0.1) 0.250.27 0.22 181 V Si_(0.2)B_(0.05)N_(0.1)C_(0.55)H_(0.02)O_(0.02)Ti_(0.06)0.19 0.22 0.23 150

indicates data missing or illegible when filed

In Example 1 to Example 7 of the invention of the hard film A, Fy/Fx wascontrolled thus changing the content in the amorphous carbon and as aresult IX/Iy was thereby changed. On the other hand, in Example 35 andExample 36, Fy/Fx was selected to get a high carbon content, resultingin a high Ix/Iy. In comparison Example 39 to Example 41, ahydrocarbon-based gas was not used in the film formation. The low carboncontent results directly from sputtering of the mixed target (SiC/BN).

For evaluating the sliding characteristics of the film A of theinvention, the coated members in Examples of the invention andcomparison Examples were tested for the friction coefficient by using aball-on-disc type frictional test. Regarding the value of the frictioncoefficient, the data from the start of sliding to the end thereof wereaveraged to be the frictional coefficient of the tested sample.

In the test, used were a φ6-ball material of SUJ2, and a disc preparedby coating a cemented carbide insert of ISO Model No. SNMN120408corresponding to K10, with a film A of the invention mostly deposited ata film B. Notice that the friction behavior is determined by the film Abecause the film A where never time fully worn during the friction test.

(Test Condition)

Sliding speed: 100 mm/sec.

Sliding radius: 3.0 mm

Load: 2 N.

Sliding distance: 50 m

Test temperature: room temperature, 300° C., 500° C.

Test atmosphere: in air, no lubrication.

The test results of the samples are shown in Table 2.

The found data of the friction coefficient in Table 2 and Table 3confirm that the film A and caused by that also the multilayer filmcoated member samples of the invention all had a friction coefficient ofμ<0.3 at room temperature, at 300° C. and at 500° C., therefore havingexcellent frictional characteristics. This is owing to the effect of thelubricity characteristics of the hard film A in those samples. From theresults, it is understood that the film coated member of the inventionhas a friction coefficient μ≦0.3 within a temperature range of from roomtemperature to 500° C. On the other hand, in comparison Examples, thefriction coefficient of all the samples could not be μ≦0.3. For example,in comparison Example 38, the friction coefficient in a high-temperaturerange was μ<0.3, but the friction coefficient at room temperature wasμ=0.7 and was high. This is because in a high-temperature environment,the added element boron exhibited its lubricating effect, but in a roomtemperature range, the element did not exhibit the effect. In comparisonExamples 42 and 43, the friction coefficient was μ<0.1 and was extremelylow at around room temperature, but in a high-temperature range, thefriction coefficient was unstable to the graphitization and oxidation ofthe film. Due to the high fluctuations at the higher temperatures (500°C.) it was difficult to give definite friction values.

The samples 35 and 36 with the highest carbon showed a similar frictionvalues like the standard DLC-coatings at 500° C.However the coating show some advantages still over the standard DLCcoatings as shown later.

The samples of Examples of the invention and Comparative Examples wereheat-treated and tested for their oxidation resistance. As the substratein the test, used was an insert of an ultra-fine particulate cementedcarbide alloy having a Co content of 8% by weight. In air under thecondition of 1000° C. and 58% humidity, the samples were kept for 2hours, and then cooled with cold air flow. After the heat treatment, thecross section of the hard film was analyzed with a scanning electronicmicroscope (hereinafter referred to as SEM), thereby measuring thethickness of the oxide layer. The oxide layer thicknesses are shown inTable 2 and Table 3. It should be mentioned that the comparison Examples42 and 43, as hard carbon coating without boron and silicon where notable to withstand the high oxidation temperature. The examples 35 and 36with the high carbon content showed still a good stability againstoxidation.

To Demonstrate the Excellent Heat-Resistance of the Film a SEM (ScanningElectron Microscope) Images are Shown

FIG. 4 and FIG. 5 SEM (scanning electron microscope) images of thesamples after heat treatment. FIG. 4 is a SEM picture of the sample ofExample 1 of the invention; and FIG. 5 is a SEM picture of the sample ofa comparison Example 38. The sample of comparison Example 38 as a hardcoating with a TiSiN coating on top has within the group of traditionalhard coatings an excellent oxidation resistance in high-temperatureenvironments. Both in FIG. 4 and FIG. 5, only the film was oxidized, andthe substrate was not oxidized. In the sample of Example 1 of theinvention in FIG. 4, only the surface layer of the film A was oxidized,and the thickness of the oxide layer was 100 nm, or that is, the oxidelayer was extremely thin. On the other hand, in the sample of comparisonExample 38 of the invention in FIG. 5, the thickness of the oxide layerwas 900 nm.

The results confirm that that the film of the invention has excellentoxidation resistance in high-temperature environments.

INDUSTRIAL APPLICABILITY

In general the inventions offers a solution within hard protectingcoating excellent in oxidation resistance and lubricity characteristics,and is therefore applicable to members that require good abrasionresistance and good high-temperature oxidation resistance such ascutting tools, molds, forming tools, engine parts, gas turbines and thelike, and also to members that require good sliding characteristics suchas automobile engine parts and the like.

Beside the single layer film consisting at least of the elements CSiB,and the two layer multilayer films consisting of a traditional hardcoating plus the film consisting at least of the elements CSiB alsomultilayer with more than one single layer of each type might bedeposited. The thicknesses of each single layer might be in thenanometer range both of the film consisting at least of the elementsCSiB and traditional hard coatings (e.g. AlTiN or AlCrMgSiN).

DESCRIPTION OF REFERENCE NUMERALS

-   1 Multilayer film coated member-   2 Substrate-   3 Hard film B-   4 Hard film A-   5 RF coating source-   6 Arc source-   7 RF coating source-   8 Arc source-   9 DC bias power or high-frequency (RF) bias power-   10 Vacuum chamber-   11 Substrate holder-   12 Vapor inlet port or vapor discharge port-   13 Coating apparatus-   14 Shutter-   15 Shutter-   16 Shutter-   17 Shutter

1. A protective coating, having the chemical compositionC_(a)Si_(b)B_(d)N_(e)O_(g)H_(l)Me_(m), wherein Me is at least one metalof the group consisting of {Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, Y, Sc,La, Ce, Nd, Pm, Sm, Pr, Mg, Co, Ni, Fe, Mn}, with a+b+d+e+g+l+m=1,characterized in that0.45≦a≦0.980.01≦b≦0.400.01≦d≦0.300≦e≦0.350≦g≦0.200≦l≦0.350≦m≦0.20
 2. A protective coating in accordance with claim 1, wherein,apart from impurities, e=0 and g=0 and l=0 and m=0.
 3. A protectivecoating in accordance with claim 1, wherein 0.56≦a≦0.81.
 4. A protectivecoating in accordance with claim 1, wherein 0.12≦b≦0.26.
 5. A protectivecoating in accordance with claim 1, wherein 0.02≦d≦0.10.
 6. A protectivecoating in accordance with claim 1, wherein 0.03≦e≦0.08.
 7. A protectivecoating in accordance with claim 1, wherein 0.01≦g≦0.06.
 8. A protectivecoating in accordance with claim 1, wherein 0.03≦l≦0.10.
 9. A protectivecoating in accordance with claim 1, wherein 0.05≦m≦0.10.
 10. Aprotective coating in accordance with claim 1, wherein a free carbon C—Cbonding is present in the hard coating.
 11. A protective coating inaccordance with claim 1, wherein a C—H bonding is present in the hardcoating.
 12. A protective coating in accordance with claim 1, whereinthe hard coating has a hardness of at least 1000 Hv to 4000 Hv.
 13. Aprotective coating in accordance with claim 1, wherein the hard coatinghas a hardness of at least 1500 to
 3500. 14. A protective coating inaccordance with claim 1, wherein a residual stress of the hard coatingis between −0.5 to −3.5 GPa.
 15. A protective coating in accordance withclaim 1, wherein the coating includes at least 2 single layers with theelements C_(a)Si_(b)B_(d)N_(e)O_(g)H_(l)Me_(m) alternating with at leastone single layer of traditional hard coatings.
 16. A coated memberhaving a protective coating in accordance with claim
 1. 17. A coatedmember, wherein a multilayer film is provided on a surface of themember, the multilayer film comprising at least a hard film (A) and ahard film (B) of different composition, wherein the hard film (A) is thelow friction carbon containing hard coating in accordance with claim 1being provided as the outermost layer of the multilayer film of thecoated member.
 18. A coated member in accordance with claim 16, whereinan additional layer is provided, the composition of which is representedby Si_(b)B_(d)C_(a)N_(e)O_(g) that satisfies a+b+d+e+g=1, 0.10≦b≦0.35,0.01≦d≦0.25, 0.45≦a≦0.85, 0.03≦e≦0.30, and 0<g≦0.20, and the hard film Bof an underlying layer below the hard film A comprises at least twometal ingredients selected from Al, Ti, Cr, Nb, W, Si, V, Zr and Mo, Mg,Co, Ni, Ce, Y, La, Sc, Pr, and at least one non-metallic ingredientselected from N, B, C, O and S.
 19. A coated member in accordance withclaim 16, wherein the coated member is a cutting tool, a mold, a formingtool, an engine parts, a component of an internal combustion engine, ora component of a gas turbine.
 20. A method for producing a protectivecoating in accordance to claim
 1. 21. A method in accordance with claim20, wherein the method is a PVD-method.
 22. A method in accordance withclaim 20, wherein the method is a RF magnetron sputtering method.
 23. Amethod in accordance with claim 20, wherein the method is a dcsputtering or a pulsed DC sputtering method.
 24. A method in accordancewith claim 20, wherein the method is a High Power Pulsed MagnetronSputtering method.
 25. A method in accordance with claim 20, wherein acomposite target is used, for RF sputtering, e.g. SiC/BN mixtures.
 26. Amethod in accordance with claim 20, wherein a carbon comprising targetwith inserts made of SiC, B₄C is used.
 27. A method in accordance withclaim 20, wherein a reactive gas comprising nitrogen is used.
 28. Amethod in accordance with claim 20, wherein a reactive gas comprising acarbon containing gas is used.
 29. A method in accordance with claim 20,wherein a reactive gas comprising a carbon containing gas and nitrogenis used.
 30. A method in accordance with claim 20, wherein an arcevaporation method is used.
 31. A method in accordance with claim 20,wherein a carbon cathode is used alloyed with Si and boron.
 32. A methodin accordance with claim 20, wherein a reactive gas is used.
 33. Amethod in accordance with claim 20, wherein a CVD method is used.
 34. Amethod in accordance with claim 20, wherein a PE-CVD methods is appliedby using a precursor comprising at least carbon, silicon and boron.